1. Field of the Invention
The present invention relates to a method and an installation for clinching pieces of sheet metal.
The clinching operation is frequently used to connect two pieces of sheet metal to each other, e.g. two metal sheet panels of a component or subassembly of the body of a vehicle, such as the structure of a vehicle door. The two metal sheet panels forming a structure of this kind are mutually joined with a clinching operation performed along the perimeter of the structure or at least along some segments of the perimeter.
According to a typical arrangement, a peripheral edge portion of one of the two pieces of sheet metal is initially bent at 90° and the corresponding edge portion of the other piece has a flat shape and is superposed to the other panel in the immediate vicinity of the edge portion bent at 90°. The clinching operation is typically conducted in two or more successive steps. In a first step, the 90° portion is initially bent towards the other panel by about 45°. In a second step, the portion bent at 45° is further bent by another angle of about 45° in order to be flattened against the edge of the other panel.
2. Description of the Related Art
European Patent Application no. 03001105.0 by the same Applicant (not yet published as of the filing date of the present application) describes a clinching tool of the roll type, mounted on the wrist of an industrial robots that moves the tool along the peripheral edge of the pieces to be clinched.
In many cases, before the clinching operation a hot-curing resin is spread along the entire perimeter or only on some localised areas of the edge to be clinched. The hot-curing resin serves as a sealant and/or structuring agent. After the clinching operation, the piece can be subjected to a heating step to cause the polymerisation of the resin. The heating operation is usually performed in a separate station, different from the station where the clinching operation was performed. A traditional solution provides for the use of an induction furnace including a heating coil which extends along the perimeter of the piece.
However, this known solution is particularly burdensome in the case of small series productions, due to the need to equip an independent heating station.